The invention is related to the field of analytical biochemistry, and more specifically to the field of quantitative proteomics.
Large scale sequencing of genomic DNA, cDNA and EST's (expressed sequence tags) has identified large numbers of genes. For some selected species, the complete genome sequences have been determined and, for others, EST sequence databases are assumed to contain sequence tags for the majority of genes for that species. For the species having complete genome sequences or substantial EST sequences available, essentially all the genes have been determined. Other genomic technologies including serial analysis of expressed genes (SAGE) and differential cDNA or oligonucleotide array analysis are capable of determining quantitative expression profiles of the expressed genes at the mRNA level in specific cells or tissues. Furthermore, comparative genomic analyses have identified genes that, if defective or aberrantly expressed, are the cause of genetic or somatic diseases.
From genomic analysis or the analysis of the expressed mRNA transcripts neither the quantity nor the structure, activity and state of modification of the translated protein products can be predicted. Recently developed mass spectrometric techniques allow the rapid identification of expressed proteins by the correlation of mass spectral data that are idiotypic for the sequence of a specific protein with the sequences contained in sequence databases.
A number of approaches have been used to address the needs of proteomics analysis, including the use of reagents that allow relative quantitation of proteins in a sample. However, none of the previously described methods can be used to determine the absolute quantity of the proteins in a sample. Furthermore, these methods do not allow the analysis to be focused on selected proteins such as those that are involved in specific diseases or those that are predicted or expected to be present based on circumstantial data or considerations.
Thus, there exists a need for reagents suitable for absolute quantitative analysis of protein samples as well as reagents suitable for analysis of selected proteins, which can be used as diagnostic or prognostic markers. The present invention satisfies these needs, and provides related advantages as well.